BCardLayout: all items are visible at start

[X512]

This is hrev54024.

When using following code to build layout, all card items are visible simultaneously at start:

BLayoutBuilder::Group<>(this, B_VERTICAL, 0)
    .AddCards()
        .GetLayout(&fCardLayout)
        .AddGroup(B_VERTICAL, 0)
            .AddGroup(B_HORIZONTAL, 0)
                .Add(fWizardView, 0)
                .Add(fIntroContainerView)
                .End()
            .End()
        .AddGroup(B_VERTICAL, 0)
            .Add(fHeaderContainerView)
            .Add(new BSeparatorView(B_HORIZONTAL))
            .AddGroup(B_VERTICAL, B_USE_DEFAULT_SPACING)
                .SetInsets(B_USE_DEFAULT_SPACING)
                .Add(fLicenseCaption1View, 0)
                .Add(new BScrollView("scrollview", fLicenseView, 0, true, true, B_PLAIN_BORDER))
                .Add(fLicenseCaption2View, 0)
                .End()
            .End()
        .End()
    .End()

Following workaround fixes problem:

fCardLayout->SetVisibleItem(1);
fCardLayout->SetVisibleItem(0);

It seems that BCardLayout don’t handle non-BView items properly.

[X512]

Related discussion: ​https://discuss.haiku-os.org/t/changing-layout-at-runtime/9374/11.